Sliding members in the form of wipers are used in transportation equipment such as vehicles, aircraft or marine vessels, and industrial machinery and equipment such as construction machinery, in order to wipe off water and fine particles adhered to their glass and other smooth surfaces. Wiper blade rubber is attached to the sliding portions of the wipers. For example, in the case of automobile windshield wipers, rainwater, snow, dust or mud and the like adhered to a glass surface are removed by a wiping operation of the wiper blade rubber with the driving of the wiper. Although resin elastomers and the like are used for the base material of wiper blade rubber in addition to rubber, it is rubber that is used most commonly.
In the case of wiping off rainwater adhered to a glass surface of an automobile and the like, together with removing dust and mud adhered to the glass surface, the wiper blade rubber serves to prevent scattering of transmitted light by creating a uniformly wet state by evenly spreading out rainwater into a uniform water film, thereby ensuring the driver's field of view. However, due to adherence of dirt or wax and the like adhered to the glass surface of an automobile and the like, unevenness occurs in the frictional state of the glass surface, thereby preventing the sliding characteristics of the wiper blade rubber from being uniform when sliding over the glass surface, and resulting in problems such as “skipping”, which occurs when the wiper blade rubber repeatedly sticks and slips over the glass surface, “streaking”, which occurs when the glass is only partially wiped resulting in the formation of lines, or “uneven wiping”, which occurs when the water film is only partially removed. In addition, problems may also occur such as “chattering”, which occurs due to skipping of the wiper blade rubber over the glass, and “squeaking”, which occurs due to the wiper blade rubber undergoing self-excited vibration and hitting the glass surface caused by sliding over a site of high friction on the glass surface. Needless to say, since the driver is required to concentrate on driving, sound produced by windshield wipers is preferably as little as possible.
Water repellency treatment has recently come to be performed on the glass surfaces of automobiles and the like. Since water is inhibited from adhering to glass surfaces that have undergone this water repellency treatment due to the water-repelling effect thereof, it becomes difficult to form a uniform water film, friction between the wiper blade rubber and the glass increases, and problems such as skipping, streaking, uneven wiping, chattering and squeaking occur. In addition, the large amount of friction between the wiper blade rubber and the glass would cause the problem of disadvantageous acceleration of the damages to the wiper blade rubber and water repellency treatment film on the glass.
In order to suppress these “skipping”, “streaking” and “uneven wiping” (to be collectively referred to as “uneven wiping”) or “chattering” and “squeaking” (to be collectively referred to as “wiping noise”), a coating agent for wiper blade rubber has been proposed in order to form a coating layer for reducing the friction between the rubber material and the glass on the surface of the base material that contacts the glass during sliding of the wiper blade (Patent Document 1).